If you buy a Riesling and if you are able to buy a German Riesling ask for the Ice Riesling.
This is a very special wine wich is harvested after the first freezing night. The wine is very tasteful and has a lovely sweet taste. The freezing does the trick it changes the grapes.
We see the harvest almost every year but I'm afraid this wine is very rare. There is always a very small section at the vineyards that is special reserved for this wine.